<template>
  <div class="pagination">
    <button :disabled='pageNo===1' @click="$emit('newPageNo',pageNo-1)">上一页</button>
    <button
     v-show="startEndPage.start>1"
     :class="{active: pageNo===1}"
     @click="$emit('newPageNo',1)"
     >
     1</button>

    <button 
    v-show="startEndPage.start>2">···</button>

    <button
    v-for="(page,index) in startEndPage.end-startEndPage.start+1"
    :key="index"
    :class="{active:pageNo===startEndPage.start+index}"
    @click="$emit('newPageNo',startEndPage.start+index)"
    >
    {{startEndPage.start+index}}
    </button>
    

    <button v-show="startEndPage.end<totalPages - 1">···</button>
    <button 
    v-show="startEndPage.end<totalPages"
    :class="{active:pageNo===totalPages}"
    @click="$emit('newPageNo', totalPages)"
    >{{totalPages}}</button>
    <button :disabled='pageNo===totalPages'
      @click="$emit('newPageNo', pageNo + 1)"
    >下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:['totalPages','pageNo','continuePage','total'],
  mounted(){
    setTimeout(()=>{
      // console.log(this.startEndPage);
    },2000)
  },
  computed:{
    /* 
      totalPages:总页数
      pageNo:当前页
      continuePage:连续页
    */
   startEndPage(){
    const {totalPages,pageNo,continuePage}=this;
     //根据当前页计算连续页
     let start=0,end=0;

      //判断总页数和连续页的多少比较
      if(totalPages<continuePage){
        // 如果总页数小于连续页数，起始是1结束是总页数
        start=1,
        end=totalPages
      }else{
         //如果总页数大于连续页
        //首先根据当前的页码,计算出连续页的开头 和 连续页的结尾
        start=pageNo- Math.floor(continuePage/2);
        end=pageNo + Math.floor(continuePage/2)

        if(start<1){
           //如果start小于1  则直接设置起始为1
           start=1;
           //如果start已经变成1了 则直接设置end为连续页长度
           end=continuePage;
        }
        if(end>totalPages){
           //如果end大于总页数,则直接设置end为总页数
           end=totalPages;
           start=totalPages - continuePage + 1
        }
      }
      return {start,end}
   }
  }
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
